The conventional bicycle cantilever brake is well-known and is constructed as disclosed in, for example, Japanese Utility Model Publication Gazette No. Sho 55-47,740. The conventional centilever brake includes a pair of cantilevers B and bent at intermediate portions thereof and supported rotatably at one of their ends through support shafts K to fixing bases fixed to, for example, a front fork H at the bicycle. A tightening shaft C is inserted into the bent portion of each cantilever B, a shoe holder E carrying a brake shoe D is inserted at a stem S thereof into a through bore formed at the shaft C. A nut tightly screws with a screw thread at the utmost end of tightening shaft C, thereby fixing the shoe holder E thereto. A hanging wire G is mounted at both ends thereof onto free ends F of the cantilevers B, and a control wire W is connected to the center of the hanging wire G through a connector J. In operation, the control wire W is pulled to rotate each cantilever B toward the wheel rim R (in the direction of the arrow X in FIG. 7) around the support shaft K to thereby brake the wheel rim R by the brake shoe D.
In the cantilever brake constructed as described above, the pivot point of the cantilever B, that is, the axis of the support shaft K is near the rim R so that the radius of gyration, when the brake shoe D exerts the braking action, is smaller than that of a rim brake or a caliper brake, whereby the repetition of braking action causes wearing at a rear portion of the braking surface L in the rotation direction of the brake shoe D as shown by the chain line in FIG. 6. As a result, the contact area of the braking surface L and rim R gradually decreases, thereby creating a problem in that the braking effect greatly deteriorates.
Also, the contact area of the braking surface L, when gradually reduced, largely applies the braking effect onto the braking surface to increase wearing of the brake shoe D per unit time, thereby creating a problem in that the durability of brake shoe D deteriorates.
Furthermore, the reduced contact area at the braking surface L causes brake shoe D to shift radially inwardly from the wheel rim R to enter between spokes, thereby creating a problem in that the spoke is occasionally broken.